The 24-hour patterns of release of growth hormone, cortisol and prolactin have been shown to be related to speific aspects of the sleep- waking cycle in humans with greatest release of these hormones during normal nocturnal sleep. The objectives of the proposed research are to continue the delineation of these relationships in normal subjects and neurological and endocrinological patients employing frequent blood sampling techniques in combination with polygraphic monitoring of sleep- waking cycles.